1. Field of the Invention
The invention relates to a thermoelectric cooler, particularly for cooling intravenous (IV) solution. More particularly, the present invention relates to a transportable, wall-outlet powered cooler which maintains IV solution for the purpose of rapidly inducing emergency therapeutic hypothermia, applicable both in an emergency room environment and in an emergency vehicle at the point of injury.
2. Description of Related Art
Interest in therapeutic hypothermia intervention continues to increase as a result of hypothermia's protective impact during ischemic events. Clinical evidence demonstrates that patients suffering severe brain trauma or ischemia from myocardial infarction or stroke have improved medical outcomes if core temperature is lowered below normal body temperature (37° C.). Hypothermia was employed during the 1980s and 1990s in a range of surgical procedures to protect the brain, heart and other vital organs from ischemia, but did not gain broad acceptance as a standard of care for specific applications. Only recently has therapeutic hypothermia generated increased interest based on several significant clinical studies. Therapeutic hypothermia may ultimately become an important therapeutic adjunct in acute stroke, acute myocardial infarction, cardiac arrest, head trauma, and specific surgical procedures requiring neuroprotection.
Currently, expanded clinical trials for therapeutic hypothermia are ongoing, and broader applications for thermal management devices are anticipated. Based on several early clinical trials, the American Heart Association published a recommendation in June of 2003 that victims of ventricular fibrillation (VF) cardiac arrest may be helped by immediate mild hypothermia. Approximately 300,000 cardiac arrest cases occur in the United States each year and about 75,000 make it to the hospital. Studies are now demonstrating that mild cooling in cardiac arrest cases improve survivals about 15% (up from 40% to 55%), and further cooling of hearts after myocardial infarction, and not just arrests/defibrillations, may also be very beneficial.
In addition to cardiac arrest, multi-center clinical trials for mild hypothermia benefits in stroke treatment are also currently ongoing in the United States. Annually, there are approximately 500,000 stroke victims in the United States that could benefit from immediate cooling treatments. Also, about 180,000 trauma deaths occur in the United States annually and 50% of these deaths occur within the first few hours, with exsanguination being the common cause. All of these cases could potentially benefit from immediate, life-saving, hypothermia protocols if a point-of-injury apparatus was available.
One method shown to be effective for quickly inducing mild hypothermia is administering cold IV solution in the form of a bolus. One or two liters of IV solution or other appropriate fluid, chilled to a range of 1° C. to 4° C., and given as a bolus, can quickly lower an individual's core temperature to 34° C. or less. The generally accepted range of mild-to-moderate hypothermia is 30° C. to 34° C., and it appears the earlier that cooling is initiated, the better the outcome. Emergency cooling could ultimately benefit the following conditions: acute myocardial infarction, stroke, traumatic hemorrhagic shock, traumatic brain injury, spinal cord injury, septic shock, neuroprotection, fever control and status epilepticus.
Portable thermoelectric coolers are widely used by motorists and outdoorsmen, plus they have a variety of medical applications. An example is shown in U.S. Pat. No. 4,326,383, which shows a lightweight, compact, portable thermoelectric refrigerator for cooling and storing perishable foods, having power provided by either a 12 volt DC automobile outlet or a 110 volt AC standard wall outlet. A further example is U.S. Pat. No. 6,799,434, which shows a battery powered, portable, thermoelectric cooler for food and beverage items, having an internally located user temperature control and display panel. Moreover, U.S. Pat. No. 6,301,901 discloses a portable thermoelectric cooler and warmer for food and beverage items, having power provided by either a 12 volt DC automobile outlet or a 110 volt AC standard wall outlet. An additional example is U.S. Pat. No. 5,217,064, which shows a portable, temperature controlled, thermoelectric storage device for pharmaceuticals, powered by rechargeable batteries and having a visual warning to indicate when contents have been out of a set temperature range for a predetermined length of time. While these devices may be appropriate for the particular purpose cited, or for general use, they would not be as suitable for the purposes of cooling and maintaining bags of IV solution at a temperature appropriate for therapeutic hypothermia.
Typical thermoelectric enclosures are insulated containers having walls upstanding from a base to define a top opening to which is mounted a removable or hinged door. Thus, such coolers are typically rectangular with two sidewalls and two end walls, and have a pivoting door extending in a horizontal plane and pivoting about a horizontal axis.
Other thermoelectric containers have a door that extends in a vertical plane and pivots about a vertical axis. Further, as in U.S. Pat. No. 6,073,789, other thermoelectric containers have a door that is mountable in multiple configurations. Many thermoelectric containers can be positioned on multiple sides which permits changing the direction in which the door pivots by simply inverting the position of the container. However, the intended use of a thermoelectric cooler often dictates supporting it in only one position that will allow internal access, such as locating the container on a shelf or in a storage compartment. Further, the container may be optimally used in only one position because of the manner stored items are maintained, such as on internal shelves or compartments.
Thermoelectric units or engines further complicate the configuration of the thermal container and its door position. Such containers are well known and include a DC thermoelectric unit which either heats or cools the interior compartment depending upon the polarity of the connection to the power source. The thermoelectric unit often includes a fan for drawing air through an air intake opening, distributing conditioned air within the compartment, and venting air to the outside through an exhaust opening, or may include both an internal fan for circulating conditioned air and a second fan for the circulating air across an external heat exchanger.
The thermoelectric unit is usually provided in one of the end walls of the container or in the door, dependent on its intended use and position. In any situation, consideration must be given to the vent openings or external heat exchanger and fan in order to provide adequate circulation. If the container is to be used as a typical ice chest or storage cooler in an automobile while traveling, configuration of the door opening and thermoelectric unit is straightforward and uncomplicated. More consideration must be given to the configuration of a thermoelectric cooler to be stored in emergency vehicles where storage on a shelf or inside a cabinet is likely, but quick access for emergency situations is still required.